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\(\dfrac{x}{4}\) = \(\dfrac{3y}{9}\) ; \(\dfrac{x}{2}\) = \(\dfrac{2z}{10}\) ⇒ \(\dfrac{x}{4}\) = \(\dfrac{2z}{20}\)
⇒ \(\dfrac{x}{4}\) = \(\dfrac{3y}{9}\) = \(\dfrac{2z}{20}\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có:
\(\dfrac{x}{4}\) = \(\dfrac{3y}{9}\) = \(\dfrac{2z}{20}\) = \(\dfrac{x+3y-2z}{4+9-20}\) = \(\dfrac{36}{-7}\)
\(x\) = - \(\dfrac{144}{7}\)
y = - \(\dfrac{144}{7}\) : 4 \(\times\) \(\dfrac{9}{3}\) = - \(\dfrac{432}{28}\)
z = - \(\dfrac{144}{7}\) : 2 \(\times\) \(\dfrac{10}{2}\) = - \(\dfrac{720}{14}\)
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f(x) = 4 => (x - 4) - 3(x+1) = 4
=> x - 4 - 3x + 3 = 4
=> x - 4 - 3x + 3 - 4 = 0
=> x - 3x - 5 = 0
=> x - 3x = 5
=> x ( 1 - 3 ) = 5
=> -2x = 5
=> x = 5/-2 = -2,5
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1,\(\dfrac{-1}{4}-\dfrac{3}{4}:x=-\dfrac{11}{36}\)
\(-\dfrac{3}{4}:x=\left(-\dfrac{1}{4}\right)-\left(-\dfrac{11}{36}\right)\)
\(-\dfrac{3}{4}:x=\dfrac{1}{18}\)
\(x=\left(-\dfrac{3}{4}\right):\left(\dfrac{1}{18}\right)\)
\(x=\dfrac{27}{2}\)
2, \(\dfrac{3}{4}x-\dfrac{1}{2}=\dfrac{3}{7}\)
\(\dfrac{3}{4}x=\dfrac{3}{7}+\dfrac{1}{2}\)
\(\dfrac{3}{4}x=\dfrac{13}{14}\)
\(x=\dfrac{13}{14}:\dfrac{3}{4}\)
\(x=\dfrac{26}{21}\)
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a.\(y=\dfrac{k}{x}\Rightarrow k=y.x=12.9=108\)
b.khi x=4 thì \(y=\dfrac{k}{x}=\dfrac{108}{4}=27\)
c.khi y=36 thì \(x=\dfrac{k}{y}=\dfrac{108}{36}=3\)
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5(x - 4)2 - 9 = 36
5(x - 4)2 = 45
(x - 4)2 = 9
\(\Rightarrow\) x - 4 = 3 hoặc x - 4 = - 3
\(\Rightarrow\) x = 7 hoặc x = 1
\(5\left(x-4\right)^2-9=36\)
\(5\left(x-4\right)^2=36+9=45\)
\(\left(x-4\right)^2=45:5=9\)
\(\left(x-4\right)^2=3^3=\left(-3\right)^2\)
Trường hợp 1: \(x-4=3\Leftrightarrow x=3+4=7\)
Trường hợp 2: \(x-4=-3\Leftrightarrow x=-3+4=1\)
Vậy x = 7 hoặc x = 1
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Ta có:\(\frac{4}{x}=\frac{5}{y}\Rightarrow\frac{x}{4}=\frac{y}{5}\)
Đặt \(\frac{x}{4}=\frac{y}{5}=k\)
\(\Rightarrow x=4k;y=5k\)
\(x+y=36\Rightarrow4k+5k=36\Rightarrow9k=36\Rightarrow k=4\)
Khi đó x=16;y=20
\(\frac{x}{4}\): \(\frac{36}{x}\)=0
\(\frac{x^2-144}{4x}\)=0
x=-12, x=12